Try and answering this.

The waves are refracted by the cornea, and again by the lens. Some of them are stopped by the iris, while other will pass through the pupil. They propagate through the vitreous humor and reach the retina, where they will be focused onto the photosensitive cells. Depending on their wavelength, they may excite cones (color sensitive) or rods (black and white). The excited cells create an action potential in the optic nerve, which is combined with the signals of other photocells into a pattern that is transmitted to the visual cortex of the brain.

Sounds more like biology than physics...

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

a and c are the answeres